Electrode holder and contact means



June 1948. c. G. H. HALLETT 2,442,409

ELECTRODE HOLDER AND CONTACT MEANS Filed June 5, 1946 4 Sheets-Sheet l June 1, 1948.

C. G. H. HALLETT ELECTRODE HOLDER AND CONTACT MEANS 4 Sheets-Sheet 2 Filed June 3, 1946 June 1, 1948. c. G. H. HALLETT 2,442,409

ELECTRODE HOLDER AND CONTACT MEANS June 1, 1948. c. G. H. HALLETT I 2,442,409

ELECTRODE HOLDER AND CONTACT MEANS 4 Sheets-Sheet 4 Filed June 3, 1946 Patented June 1, 1948 2,442,409 ELECTRODE HOLDER AND CONTACT MEANS Charles Gordon Heys Hallett, London, assignor to The Morgan Crucible England, Company Limited, London, England, a company of Great Britain Application June 3, 1946, Serial No. 673,967 In Great Britain January 19, 1945 Claims. (Cl. 314-129) This invention relates to improvements in the contacts which carry the current into the electrodes in arc lamps, electric welding machines and the like.

One form of contact normally used for carrying the current into the arc lamp carbons consists of rectangular metal blocks which slide in rectangular slots in the carbon holder and press radiallyonto the side of the carbon. Either one or two blocks are commonl used. When one block is used it forces the carbon against the side of the holder from which majority of the current. In some cases the contact blocks are fitted with copper leads to convey the current, but in other cases they are used merely as pressure blocks.

The above mentioned arrangement has proved suitable for normal currents, e. g. of the order of 150 amps. but they are not capable of dealing with exceptionally heavy currents. For normal currents it is normally necessary to employ some special metal, such as Monel metal, which will not readily oxidize. The contacts become very much heated because the resistance of the carbon electrode is high and considerable heat is generated by the passage of the current. The contact between the rectangular block and the slotin which it slides is poor, and at heavy currents the cooling of the contact block presents a very difficult problem.

The improvement according to the present invention overcomes the difiiculties outlined above, and provides an arrangement which can be used satisfactorily with very high current densities which may be six or more times those normally used, and which I can produce with a "wind drawn arc, i. e. an are along which a highvelocity air blast is blown and drawn away.

The arrangement according to the invention ensures that the contact between the contact block and the electrode holder is of the same quality as that between the contact block and the electrode.

In accordance with the invention a contact block for an electrode of an arc lamp and the like has a wedge form coacting with a sloping surface of the electrode holder, so that an axial causes it to bear with pressure upon that produce the wedge action,

direction.

An ordinary simple form of wedge may be employed in the construction of the contact block but the angle of such wedge will require careful selection. If the angle is too acute the wedge may be liable to jam, whereas if the wedge angle is increased to, say, to make jamming impossible, the wedge may be inconveniently large and diificult to make stable.

This difficulty may be vercome, according to a preferred feature of the invention, by constructing the contact block as a series of Wedge elements, one behind the other, the electrode holder being formed with a corresponding series of co acting sloping surfaces. The wedge elements of the series are preferably formed as an integral unit. In effect, therefore, the back of the contact block, i. e. the face opposite that which bears on the electrode, has a serrated formation, and the surface of the electrode holder is correspondingly serrated. The back of the contact block may be plane, except for serrations transverse to its length forming a series of wedge faces,cr, alternatively, it may be of cylindrical or conical form-coaxial with the axis of the electrode and serrated with circular, or substantially circular, grooves.

This latter case may be developed to produce a most practical and useful form of contact block when there is a plurality of contact blocks surrounding the electrode. This consists in forming the several surfaces of the Wedge elements of the several blocks so as substantially to produce a helical formation matching a helical thread in the electrode holder. The contact blocks may accordingly be severally produced by dividing a bolt along its length into segmental laws, The bolt may be screw-threaded externally to match an internal screw-thread in the electrode holder and may be centrally bored to accommodate the electrode, preferably to the precise diameter of the electrode. Each segmental jaw constitutes a contact block and the assembly of the several complementary blocks is screwed into the thread hole in the electrode holder. The material cut or sawed away from the bolt when dividing it into segments permits the gripping of the segmental jaws upon the electrode whilst slackness of fit in the threaded electrode holder provides the necessary freedom of movement of the segmental jaws in the electrode holder to allow the wedging action to function.

The employment of contacts in the form of wedges may require that the friction between the electrode and the wedge or wedges should be taken into account in order that there shall not '1 andB be an undue variation of the pressure of the wedge contact upon the surfaces that it engages, having regard to the external pressure due to friction when the electrode is fed forward, and the reduction of pressure when the electrode is retracted, e. g. on account of overfeeding, a,

Therefore, according to a further feature of the invention, the electrode feeding means may be mounted and arranged so that the reaction force thereon from the electrode is transmitted to counteract axial thrust on the contact block or and the amount of which is dependent on the friction betweenithecontact block 3 and the elecblocks due to friction between thesamegnd the electrode being fed. The electrodefeeding ineatis; may therefore be mounted on a floating-support;

or carriage opposing, when it is ,rearwardly urged as the feeding means drives the electrode for;

ward; spring pressure or other yielding. axial thrust transmitted to the contact block or blocks. The floating support or carriage may accordinglyl be the intermediary through which the yieldin r st s m t d; q

3 With such an arrangement, when the electrode rfedforward its frictional forward urge on the wedge contact, orcontacts is: counteracted-by a rearward reactivejorce fromthe electrode driving means, In. this waythe contact pressure is maintained substantially constant .at the pressure due to that which is imposed upon itcbnforeirample,

a compression spring or sp'rings bearing thereon,

despite changes of friction.

.The invention is illustrated, by way-of example, in the accompanyingdrawings, in which:

, Figure 1 is a diagrammatic sectional elevation illustrative of the principle underlying the invention;. QM, .Figure 2 is a section on the'line 2-2 of Figure1;.'i 'l ,7 Figure 3 is a diagrammatic sectional elevation showing aslight modification of Figure 1; Figure 4 is a section on the line 4-4 of Figu re3;.,;. .l. V Figure 5 is a section on the line 5--5 of Figures Figure 61 shows a modification of a detail of Figure l or 3, in sectional elevation;

Figure? and Figure 8 are alternative sect-ions taken on the line 8- 7, 8 of Figure 6.

Figure 9 is asectional elevatio n of a practical f orm of construction according to the invention; Figure l0 is a horizontal' central section of a tof i 9;

Figure ll is a section taken on the line l'l-,ll fis r 9; 1

a Figure; 12 is a section taken on the line l2--!2 ure 9 j-, n, t

:E ure s n en zvi w, of a det i o F gu eii: Figure 14 is a detail in section to an enlarged Referring to Eigures 1 2 and.5 of the drawings,

1 is .the electrode holder, the electrode and 3 V a contact block, dis ,a toothedfeedingwheel in driving engagement. with, the electrode 2. ,This

fee d wheelis mounted on a bush 5. secured toLa spindle-Son oneend of which is'm ount'ed aworm hee .1 d ghts r mit-1 .T w i i c rried his. pi e, m ted as-.: h w :i brackets id projecting from the casing-of the electrode iholcier. 1.: .A tens o pr n H cone nec'ted'tothe spindle it urges the feed wheel 4 into driving engagementwith the electrode. 2.

, T-he spindlet isrotatablymoimted in a double or forked link-1E2, the. forwardend of which :is

trode 2, is opposed to the thrust from the spring I3, and; accordin ly relieves the contact block 3 gof excess'ivezthrust which might cause jamming and which, in effect, maintains the friction between the electrode and the contact block substantially constant.

Itwill also be noted that an equally good contact isproduced as between the contact block and the electrode holder as between the contact block andthe electrodejsorthatnotpnly is rthere established. the proper electrical ,coi'inctioh between the ,electro de, holder and the electrode, {the electrode holder being connected totheelecttical supply) but there is ensured ,a good? thermal contact ,between the contact blocliandjth'e electrode holder tonca rry, away f roirigthe contact block the'great'heat tojwhich'itisf jedtcdaliiil transfer it tofthe. electrode holder will normally be watercjooled. one, to thrsatisfaciery thermal. contact. w ion; is established. according to theinvention between a r r x the electrodeholder therejniayhe'employeii ch larger currents than'have, hithertdbeen possible.

Figures Band 4'sifrerntmrigures'ranu zfin 7 that the worm 8 is mountedjinlhearings carried by the. link J2, instead, ofgheing car'ried in brackets,extending, frornf the. electrode Accordingly in this case the drivingltj 2 the worm'tionjthe worm wheel ldoesj 110 .f

inoppqsition tothe spring13asit-do sinthe construction."illustrated Figures 1. nd', 2 ,In this connection, referringbacKtoFi hYes. ran-r12,

itm-ay he arranged bymoiinti'ng the worm" 51.011 7 m incimationmine,norizoiita1,;,th t1t eiw rm thrust on, the wonin wheel ,1 .alugfiients .the if roe exerted bythe' spring 1 to ress the reed. when unch the electrodeZ so'that when the fri'ctioh between the oestrous of th" gntact blockin creases, the pressure of thefeedwhel q i', the

electrode will likwise increase and so. prevent slipping, V appreciate It will'be a. a: that, other, seats a drive ,to, the feed wheel m ay be employed W310i instance, in rthe case shown infliiguresl arr (11a there'maik be emplyed a bevel, wheeled drive pivotally connected with the c'ontactblock 3,,and

whilst in thezoasetofj, Figures 3 and .4, thesanv e,

may be by bevelwheelsor may bettralnsmit ed direct to,the. spindle of the feed wheel by means of aflei zibl e'shaft.. t 1

Figure 6: illustrates, a contact; block, which is serratedso as to produce .aseries" ofwedge I-. ments as hereinbefor'e' referred to. 'llf-he'lc'ont ct serrations l 5 which'loosely fitginto'corresponding' serrations, 116 in the elctrodeholder tl Itiiiiilf be seen t at thisjori structi'on is ,equivalent t'o ,as'infgleio din'arywedg'e V with a largeslope;butaccoinmodatedin' a much smaller tabs, U Figure '7 shows o efor'm of sectionof the cone tafit b ck fi'har ne i t i cas s straightback which would be locatedin a rectangular recess in theelectrodeholder i. 3 V Figure 3, on the othenhand, shows an alterna-' tive section illustrating the provision of three its driving engagement with the electrode 2,

the. .contactj,bloclfarid serrated contact blocks forming complementarily a cylindrical section accommodated in a circular bore in the electrode holder In the practical form of construction about to be described the complementary segmental form of contact block is employed.

It will be appreciated in regard to the diagrammatic forms shown in Figures 1 to 7 that although only one contact block is shown as bearing on the electrode, there may be disposed two or more, preferably three, such contact blocks at equal angular spacings around the electrode.

Referring now to Figures 9 to 12, the electrode holder casing is indicated at 28 and within this is mounted the electrode feeding means whilst the contact blocks, which will be described hereafter, are mounted in a detachable nose piece 2|; the electrode is indicated by the reference numeral 22.

The drive for the electrode feeding means is from a shaft 23 which drives, through gear 24, 2 an articulated shaft 26 having a forward hearing at 21. In front of the bearing 2'! the shaft carries a worm 28. This worm 28 drives (see Figure 11) a pair of worm wheels 29, 39. These worm wheels are splined on spindles on which, respectively, are splined electrode feed wheels 3|, 32. The feed wheels 3| 32, each have two toothed elements 33, 33, and 34, 34, which engage the electrode 22. The spindles of the respective feed wheels 3|, 32, are carried by frames 35, 3B, pivoted at 31, 38, and urged to press the feed wheels upon the electrode by compression springs 39, 40.

The contact blocks (see Figure 13) are complementary segments 4| of a cylindrical bolt which is threaded at 42 and screwed into the bore of the electrode holder nose piece 2| which is threaded as shown at 43. Figure 14 shows the matching thread forms of one of the contact segments 4| and the electrode holder 2| an illustrates the wedging action. The wedge slope in this case is 7 49.

The rear ends of the contact block segments 4| are formed as shown in Figures 9 and 13 with projections 44. These projections serve as gimbals engaging recess 45 in a ring 46 mounted at the head of a carriage structure 47 which supports the electrode feeding means hereinbefore described. The carriage structure 41 at its rear end is slidably mounted on a tube 48 and is thus a floating carriage. A main compression spring 49 is interposed between a shoulder on the carriage 41 and a rear cap 5|! and thus serves to exert, through the intermediary of the carriage 41, an axial thrust upon the contact block segments 4|, bringing the wedge action into play and causing the contact block segments 4| to bear upon the electrode and the sloping surfaces of the teeth 42 of the contact blocks to bear with like pressure upon the sloping surfaces of the teeth 43' of the electrode holder as has hereinbefore been explained. The reaction thrust from the drive between the feed wheels 33, 34, and the electrode will be rearwardly transmitted by the carriage 41 to oppose the force of the spring 49, thus maintaining the wedge pressure substantially constant notwithstanding changes of friction between the contact block segments 4| and the electrode 22.

The part marked 5| in Figure 9 is a trip lever having a. nose 52 bearing on the electrode 22 and a tail carrying a contact 53 cooperating with a contact 54 and coming into engagement therewith when the tail end of the electrode 22, in the course of consumption, passes beyond the nose 52, the spring 55 then causing the lever 5| to trip.

The contacts 53, 54 may be connected in an electrical circuit adapted, when closed, to give an indication showing that the electrode. has been: nearly consumed.

It will be seen from Figure 9 that the electrode holder nose piece 2| has passages 55 for the circulation of cooling water which is supplied at the.- union marked 51 and discharged through a simi-- lar union not seen in the drawing. Due to the good thermal contact between the contact block: segments and the electrode holder the very great heat developed in the contact block segments, es-' pecially when large currents for which the present device is adapted are employed, is dissipated by transfer to the water cooled electrode holder 2| What I claim is:

l. The combination of an electrode, an electrode holder, and at least one contact block interposed between the electrode and electrode holder, the contact block comprising a series of Wedge elements, one behind another, and the electrode holder being formed with a corresponding series of coacting surfaces.

2. The combination of an electrode, an electrode holder, and at least one contact block interposed between the electrode and electrode holder, the contact block comprising an integral series of wedge elements, one behind another, and the electrod holder being formed with a corresponding series of coacting surfaces.

3. The combination of an electrode, an electrode holder, and a plurality of complementary contact blocks surrounding the electrode and interposed between the electrode and the electrode holder, each contact block having a series of surfaces sloping towards the electrodes which in the assembly of contact blocks produce a helical formation and the electrode holder having a helical thread matching said helical formation.

4. The combination of an electrode, an electrode holder, a plurality of complementary contact blocks surrounding the electrode and interposed between the electrode and the electrode holder, each contact block having a series of surfaces sloping towards the electrode which in the assembly of contact blocks produce a helical formation and the electrode holder having a helical thread matching said helical formation, and means for applying an axial thrust to the contact blocks.

5. The combination of an electrode, an electrode holder, electrode feeding means, at least one contact block interposed between the electrode and electrode holder, the contact block and the electrode holder having engaging surfaces sloping towards the electrode, means for applying an axial thrust to the contact block, and a connection between said means and said electrode feeding means for transmitting reaction upon the latter by the electrode to oppose the said axial thrust.

6. In an arc lamp or the like the combination of an electrode, an electrode holder, electrode feeding means, at least one contact block interposed between the electrode and electrode holder, the contact block and the electrode holder having engaging surfaces sloping towards the electrode, means for applying an axial thrust to the contact block. a floating support for the electrode feeding means, and means connecting said floating support with the said means which applies the axial thrust.

7. In an arc lamp or the like the combination of an electrode, an electrode holder, electrode 7 feeding-1 means; at least onecontact block-inter pd'sedbtween the electrodeand electrode holder, the coritact'hlock'and the electrode'holder having engaging surfaces sloping towards the el'ec trode; a floating support for the electrode feeding means, and means "applying axial thrust to the contact blockthrough the intermediary of the flcatingsupport.

8. Inan' arc lamp or the like the combination oi." a'n'eleetrode; an electrode holder, electrode feedingmeans, at'le'ast one contact blockinterp'osed' between the electrode and electrode holder, th'ecbntact' block and the electrode holder having engagingsurfaces sloping towards the electrode, a floating support for the electrode feeding means, and spring means applying axial thrust to the contact block through'the intermediary of the floating support.

91 The: combination of an electrode, an electrodeholder, and at'least one contact block interposed b' tween the electrode and electrode holder, the "contact block having a longitudinally grooved electrode engaging surface on one'side and a series of longitudinally spaced Wedge elements on its" opposite side, said Wedge elements being adapted to coact with a corresponding: series-of wedge surfaces on said electrode-holder} 10; The-combination of an electrode, an elec trode holder, and a plurality of-complementary contact blocks surrounding the electrode'afid interposed between the electrode and the electrode holder, each contact block having a longitudinally grooved electrode engaging surface ononeside and a series of longitudinally spaced wedge-sui faces sloping towardthe electrode-on its' opposite side," said contact'lolccks when assembled;- producing a helical formation, and'the electrode holder having'a'helical thread, matching said helical formation and adapted to coact therewith? CHARLES GORDON HEYS HALLETT.

anrnn'encns omen The iollowingreierences are of recordin the file of this patent:

UNITED STATES PATENTS 

